The oligomerization of olefins is known in the art, such oligomerization processes being effected by treating olefinic hydrocarbons with certain catalysts to obtain various oligomers which will find a useful function in the chemical art. One type of catalyst which may be employed for this particular type of reaction comprises a supported metal compound. For example, U.S. Pat. No. 3,562,351 discloses a method for dimerizing olefins utilizing a supported catalyst which has been prepared by impregnating a suitable support with a salt solution of a Group VIII metal followed by a heat treatment in an inert atmosphere at a temperature less than that which is required to form a metal oxide but which will form a complex on the surface of the solid support. Following this, the catalyst is activated by treatment with an organometallic compound. U.S. Pat. No. 3,483,269 describes a catalyst useful for oligomerizing lower olefins which comprises a .pi.-allyl nickel halide supported on an acidic inorganic oxide support. If so desired, the support may have been optionally treated with an alkyl aluminum compound. U.S. Pat. No. 3,592,869 also describes a catalyst which is useful for the oligomerization of olefins. A divalent nickel compound and an alkyl aluminum compound are contacted with an olefinic compound. The resulting mixture is then used to impregnate an inorganic refractory oxide support. Another patent, namely U.S. Pat. No. 3,644,564, describes a catalyst for the oligomerization of ethylene which comprises an organo aluminum-free reaction product of a nickel compound which is an atom of nickel in complex with an olefinically unsaturated compound and a fluorine-containing ligand. The catalysts are typically formed in situ. U.S. Pat. No. 3,679,772 describes a process for reacting monoolefins with diolefins, the catalyst for such a reaction comprising a complex of (1) nickel, (2) a Group VA electron donor ligand such as an organophosphine, (3) a nonprotonic Lewis acid and (4) a reducing agent which itself may be a Lewis acid, all of which are composited on an acidic silica-based support.
U.S. Pat. No. 3,697,617 describes an oligomerization process involving the use of a catalyst comprising a complex of nickel with a chloro-containing electron donor ligand such as chlorodiphenylphosphine combined with a nonprotonic Lewis acid which is capable of forming a coordination bond with nickel and a reducing agent capable of reducing nickel acetylacetonate to an oxidation state less than 2. This complex may be composited on a solid support comprising an acidic silica-based material such as silica-alumina. The Lewis acid and the reducing agent may comprise the same compound as, for example, ethyl aluminum sesqui chloride. U.S. Pat. No. 3,663,451 describes a catalyst which is obtained by reacting a transition metal halide such as nickel halide with a carrier to give a carrier-metal bond. This product is then reacted with a ligand such as a phosphine or .beta. ketone and finally activated by treatment with an aluminum alkyl or chloro alkyl.
U.S. Pat. No. 3,755,490 describes the polymerization of an olefin utilizing a catalyst comprising nickel, a Group VA electron donor ligand, a Lewis acid, and a reducing agent on a solid acidic silica-based support. U.S. Pat. No. 3,954,668 is drawn to an oligomerization catalyst comprising a nickel compound, a chloro-containing electron donor ligand, or a phosphorous compound, a nonprotonic Lewis acid reducing agent which is capable of reducing nickel acetylacetonate to an oxidation state of less than 2 and which is also capable of forming a coordination bond with a nickel. U.S. Pat. No. 3,170,904 speaks to a catalyst which is useful for polymerization comprising a large surface area metal of Groups VIIA or VIII of the Periodic Table, boron trifluoride etherate, an organometallic compound of Groups I, II, III or IV or a halo derivative of an organometallic compound of Groups II, III or IV or a hydride of a metal of Groups I, II or III. The large surface area metal which comprises one component of this catalyst is in metallic form as, for example, Raney nickel. If so desired, the catalyst may be composited on a diatomaceous earth carrier. In like manner, U.S. Pat. No. 3,170,904 discloses a catalyst which comprises (A) a carrier-supported nickel or cobalt oxide which has been prepared by impregnating the carrier with the hydroxide, organic acid salt, inorganic acid salt, followed by oxidation in the presence of oxygen or a combination of nitrogen and oxygen; (B) a boron, titanium, zirconium, or vanadium halide; and (C) an alkyl metal or alkyl metal halide. In addition to these patents, British Patent No. 1,390,530 describes an oligomerization catalyst which has been prepared by thermally pretreating a metal oxide carrier material followed by reacting with a halogen-containing organo-aluminum compound and thereafter in a step-wise fashion, impregnating this product with a divalent nickel or cobalt complex at temperatures ranging from -50.degree. to 150.degree. C.
As will hereinafter be shown in greater detail, the oligomerization of olefinic hydrocarbons may be accomplished by treating said olefins in the presence of a catalyst which has been prepared in a manner such that the catalyst will remain active and stable for a relatively long period of time and, in addition, will provide products which possess a desired configuration with respect to the branching or minimal branching of the chain.